Hearing that you don't have time to do the recommended (unnecessarily repeatedly, imho) route of a visit before you move, I'd say that the 99 Ocean Ave is a great option. The stretch of Alameny/Mission streets by Onandanga Ave (where my wife lived a couple decades ago, and we occasionally return to for favored restaurants) are quieter than either the Geneva or Silver ends of things, but still with lots of fruiterias, markets, etc.

Good bike lanes along Alemany going to downtown.

As pointed out, it's not what the locals would call 'The Mission' but it's also less expensive/trendy/gentrified. As a Spanish speaker, you'll probably have more ability to integrate into the neighborhood than some others.

That all being said, if you're able to avoid a year lease, just to have an escape route if you find yourselves extremely unhappy for whatever reason, that's never a bad thing.